Add type validations for function imports (#8478)

Validates that the exported function is a subtype of the import
declaration. Part of #8261.

Example error:

```wast
(module $A
  (func $f (export "f") (param i32) (result i32)
    (local.get 0)
  )
)

(register "A" $A)

(module $B
  (func (import "A" "f") (result i32))
)

;; [trap Imported function A.f with type (func (param i32) (result i32)) isn't compatible with import declaration with type (modulo rec groups): (func (result i32))]
```